Sounds like a homework question, so going to try and help but also lead you a bit towards the answer.

So both were divided due to warfare and resolution. Germany and Berlin as a result of the Second World War and Korea as a result of the Korean War.

The Cold War was the period which started immediately after the Second World War and lasted until the 1990s (to put a convenient end date, though you could put it earlier, or much much later to not at all).

The Cold War saw world powers vying for control, and for influence over other nations. These groups tended to unify -- either through actual agreements or just simply convenance -- and to keep it simple we refer to the two sides as First World and Second World.

The First World were the US, and NATO allies. The Second World were the Soviets, China, and their allies. There is also the "Third World" which refers to those unaligned with either side.

See this map for First World in blue, Second world in Red. Look at where Germany is split: how could this create tensions? Look at Korea, how could this create tensions? https://en.wikipedia.org/wiki/First_World#/media/File:Cold_War_alliances_mid-1975.svg

...because they were divided by the Cold War? The USSR occupied East Germany and created the DDR, and a section of Berlin (which was located within the DDR). Korea was divided between the USSR and USA and the two sections of the country were encouraged to develop in different ways by the occupying nations.

This is a little flippant, but actually does have some historical truth to it. Korea got divided up b/c National Geographic had published a map that folded in half along the 38th parallel.https://nationalinterest.org/blog/the-buzz/how-2-colonels-national-geographic-map-divided-korea-24734

Conversely, why did these countries become divided, but China and Taiwan did not?